import converter from './converter.js';

import prepare from './_prepare.js';

import { getMode } from './modes.js';

import { differenceEuclidean } from './difference.js';

const rgb = converter('rgb');

const fixup_rgb = c => {

const res = {

mode: c.mode,

r: Math.max(0, Math.min(c.r !== undefined ? c.r : 0, 1)),

g: Math.max(0, Math.min(c.g !== undefined ? c.g : 0, 1)),

b: Math.max(0, Math.min(c.b !== undefined ? c.b : 0, 1))

};

if (c.alpha !== undefined) {

res.alpha = c.alpha;

}

return res;

};

const to_displayable_srgb = c => fixup_rgb(rgb(c));

const inrange_rgb = c => {

return (

c !== undefined &&

(c.r === undefined || (c.r >= 0 && c.r <= 1)) &&

(c.g === undefined || (c.g >= 0 && c.g <= 1)) &&

(c.b === undefined || (c.b >= 0 && c.b <= 1))

);

};

/*

Returns whether the color is in the sRGB gamut.

*/

export function displayable(color) {

return inrange_rgb(rgb(color));

}

/*

Given a color space `mode`, returns a function

with which to check whether a color is

in that color space's gamut.

*/

export function inGamut(mode = 'rgb') {

const { gamut } = getMode(mode);

if (!gamut) {

return color => true;

}

const conv = converter(typeof gamut === 'string' ? gamut : mode);

return color => inrange_rgb(conv(color));

}

/*

Obtain a color that's in the sRGB gamut

by converting it to sRGB and clipping the channel values

so that they're within the [0, 1] range.

The result is returned in the color's original color space.

*/

export function clampRgb(color) {

color = prepare(color);

// if the color is undefined or displayable, return it directly

if (color === undefined || displayable(color)) return color;

// keep track of color's original mode

let conv = converter(color.mode);

return conv(to_displayable_srgb(color));

}

/*

Given the `mode` color space, returns a function

with which to obtain a color that's in gamut for

the `mode` color space by clipping the channel values

so that they fit in their respective ranges.

It's similar to `clampRgb`, but works for any

bounded color space (RGB or not) for which

any combination of in-range channel values

produces an in-gamut color.

*/

export function clampGamut(mode = 'rgb') {

const { gamut } = getMode(mode);

if (!gamut) {

return color => prepare(color);

}

const destMode = typeof gamut === 'string' ? gamut : mode;

const destConv = converter(destMode);

const inDestGamut = inGamut(destMode);

return color => {

const original = prepare(color);

if (!original) {

return undefined;

}

const converted = destConv(original);

if (inDestGamut(converted)) {

return original;

}

const clamped = fixup_rgb(converted);

if (original.mode === clamped.mode) {

return clamped;

}

return converter(original.mode)(clamped);

};

}

/*

Obtain a color that’s in a RGB gamut (by default sRGB)

by first converting it to `mode` and then finding

the greatest chroma value that fits the gamut.

By default, the CIELCh color space is used,

but any color that has a chroma component will do.

The result is returned in the color's original color space.

*/

export function clampChroma(color, mode = 'lch', rgbGamut = 'rgb') {

color = prepare(color);

let inDestinationGamut =

rgbGamut === 'rgb' ? displayable : inGamut(rgbGamut);

let clipToGamut =

rgbGamut === 'rgb' ? to_displayable_srgb : clampGamut(rgbGamut);

// if the color is undefined or displayable, return it directly

if (color === undefined || inDestinationGamut(color)) return color;

// keep track of color's original mode

let conv = converter(color.mode);

// convert to the provided `mode` for clamping

color = converter(mode)(color);

// try with chroma = 0

let clamped = { ...color, c: 0 };

// if not even chroma = 0 is displayable

// fall back to RGB clamping

if (!inDestinationGamut(clamped)) {

return conv(clipToGamut(clamped));

}

// By this time we know chroma = 0 is displayable and our current chroma is not.

// Find the displayable chroma through the bisection method.

let start = 0;

let end = color.c !== undefined ? color.c : 0;

let range = getMode(mode).ranges.c;

let resolution = (range[1] - range[0]) / Math.pow(2, 13);

let _last_good_c = clamped.c;

while (end - start > resolution) {

clamped.c = start + (end - start) * 0.5;

if (inDestinationGamut(clamped)) {

_last_good_c = clamped.c;

start = clamped.c;

} else {

end = clamped.c;

}

}

return conv(

inDestinationGamut(clamped) ? clamped : { ...clamped, c: _last_good_c }

);

}

/*

Obtain a color that's in the `dest` gamut,

by first converting it to the `mode` color space

and then finding the largest chroma that's in gamut,

similar to `clampChroma`.

The color returned is in the `dest` color space.

To address the shortcomings of `clampChroma`, which can

sometimes produce colors more desaturated than necessary,

the test used in the binary search is replaced with

"is color is roughly in gamut", by comparing the candidate

to the clipped version (obtained with `clampGamut`).

The test passes if the colors are not too dissimilar,

judged by the `delta` color difference function

and an associated `jnd` just-noticeable difference value.

The default arguments for this function correspond to the

gamut mapping algorithm defined in CSS Color Level 4:

https://drafts.csswg.org/css-color/#css-gamut-mapping

To disable the “roughly in gamut” part, pass either

`null` for the `delta` parameter, or zero for `jnd`.

*/

export function toGamut(

dest = 'rgb',

mode = 'oklch',

delta = differenceEuclidean('oklch'),

jnd = 0.02

) {

const destConv = converter(dest);

const destMode = getMode(dest);

if (!destMode.gamut) {

return color => destConv(color);

}

const inDestinationGamut = inGamut(dest);

const clipToGamut = clampGamut(dest);

const ucs = converter(mode);

const { ranges } = getMode(mode);

if (!ranges.l || !ranges.c) {

throw new Error('LCH-like space expected');

}

return color => {

color = prepare(color);

if (color === undefined) {

return undefined;

}

const candidate = { ...ucs(color) };

// account for missing components

if (candidate.l === undefined) candidate.l = 0;

if (candidate.c === undefined) candidate.c = 0;

if (candidate.l >= ranges.l[1]) {

const res = { ...destMode.white, mode: dest };

if (color.alpha !== undefined) {

res.alpha = color.alpha;

}

return res;

}

if (candidate.l <= ranges.l[0]) {

const res = { ...destMode.black, mode: dest };

if (color.alpha !== undefined) {

res.alpha = color.alpha;

}

return res;

}

if (inDestinationGamut(candidate)) {

return destConv(candidate);

}

let start = 0;

let end = candidate.c;

let epsilon = (ranges.c[1] - ranges.c[0]) / 4000; // 0.0001 for oklch()

let clipped = clipToGamut(candidate);

while (end - start > epsilon) {

candidate.c = (start + end) * 0.5;

clipped = clipToGamut(candidate);

if (

inDestinationGamut(candidate) ||

(delta && jnd > 0 && delta(candidate, clipped) <= jnd)

) {

start = candidate.c;

} else {

end = candidate.c;

}

}

return destConv(inDestinationGamut(candidate) ? candidate : clipped);

};

}